GRADATION, GROWTH, SUCCESSION, DISTRIBUTION. 181 



Carnivora, the Seals, the Plantigrades, and the Digitigrades 

 exemplify the same coincidence between higher and higher 

 representatives of the same types, and the embryonic 

 changes through which the highest pass successively. 



No more complete evidence can be needed to show that 

 there exists throughout the animal kingdom the closest 

 correspondence between the gradation of their types and 

 the embryonic changes their respective representatives ex- 

 hibit throughout. And yet what genetic relation can there 

 exist between the Pentacrinus of the West Indies and the 

 Comatulce found in every sea ; what between the embryos 

 of Spatangoids and those of Echinoids, and between the 

 former and the adult Echinus ; what between the larva of 

 a Crab and our Lobsters ; what between the Caterpillar 

 of a Papilio and an adult Tinea, or an adult Sphinx ; 

 what between the Tadpole of a Toad and our Menobran- 

 chus ; what between a young Dog and our Seals, unless it 

 be the plan designed by an intelligent Creator ? 



SECTION XXVIIL 



RELATIONS BETWEEN THE STRUCTURE, THE EMBRYONIC GROWTH, 

 THE GEOLOGICAL SUCCESSION, AND THE GEOGRAPHICAL DIS- 

 TRIBUTION OF ANIMALS. 



It requires unusual comprehensiveness of view to per- 

 ceive the order prevailing in the geographical distribution 

 of animals. We need not wonder, therefore, that this 

 branch of Zoology is so far behind the other divisions of 

 that science. Nor need we wonder at the fact that the 

 geographical distribution of plants is so much better 

 known than that of animals, when we consider how 

 marked a feature the vegetable carpet which covers the 

 surface of our globe is, when compared with the little 



